1. Field of the Invention
The present invention relates generally to an image searching system for finding an image that resembles a specified image from among images managed by the image searching system where the search criteria are determined from the specified image. The present invention relates more specifically to an image searching system for finding an image based on a plurality of specified images.
2. Description of the Related Art
Images stored to a database for managing image data are typically stored with additional information that can be used to specify search conditions, including search keys, such as identifying keywords and image color keys, and image features, such as information on the shapes and colors appearing in the image. Using this common type of image database, it is possible to search the stored images to find an image similar to a user-specified image.
Image similarity in similar-image searching is determined based on such feature quantities as image shape, texture, and color. More specifically, the user specifies an image in the image database that is similar to a desired image to be searched for. Feature quantities are then extracted from the image selected by the user as the search key (referred to below as the “key image”), and the extracted feature quantities are then compared with the feature quantities registered in the image database. Image similarity indicative of the similarity between the key image and a found image is then calculated. Information on any stored image determined to resemble the key image based on this calculated image similarity is then returned as the search result.
Usually there is only one key image selected by the user, and it is often impossible to find the one image sought by the user based on the feature quantities defined from a single key image. Search accuracy is therefore often low. This can happen, for example, when there are plural features in a single image and the user focuses on only one feature, that is, when the user's search criteria are narrower than the criteria that can be extracted from the key image, as well as when numerous search conditions are specified to broaden the range of the search.
Japanese Patent Laid-Open Publication 7-65169 teaches one method proposing to solve this problem. According to the taught method, a plurality of key images is specified, a specific area in each of the key images is selected, and the features to be used as search criteria are extracted from the selected areas. The search is then conducted using these features from plural selected areas in plural images. This method thus makes it possible to search for images having all of the features found in the specified areas of the plural key images. In other words, this method enables the user to specify a wide range of search conditions based on plural images.
The drawback to said taught method is that the user is required to specify in each of the selected key images those features that are to be used for searching, and this task becomes increasingly difficult and time-consuming as the number of key images increases and the variety of selected features increases.
The present invention is therefore directed to an image searching system and an image searching method for reducing the user burden and improving search accuracy when a plurality of key images is specified and a desired image is searched for based on these selected key images.
The present invention is further directed to a recording medium for storing an image searching program embodying the image searching method of the present invention.